Extraction of Hops by Solution



Mr. Edward F Light in the Chair.

The following papers were read and discussed:—

Note on the Extraction of Hops by Solutions of Various Mineral Salts.

                                                           by John Heron, B.E., F.LC, F.C.S.

The following experiments were undertaken some years ago with a view to getting some definite idea of the action of the various salts occurring in brewing waters upon hops.  Both as regards the extractive properties of these salts, as well as the flavour and colour of the extracts so obtained, several experiments were made of which there is no occasion to give a detailed account, I have therefore taken the mean values of such experiments, which are given in the annexed table.

The method of experiment was as follows:—

The dry salts were added to distilled water at the rate of 21 grains per gallon or 0·3 gram per litre, 10 grams of hops were then digested with 900 c.c. of each solution in a boiling water bath for one hour cooled down to ordinary temperature and made up to 1,005 c.c. (10 grams of hops being found to be equivalent in bulk to 5 c.c. of water), shaken well up and filtered as bright as possible, 100 c.c. contained the extract of 1 gram of hops, this quantity was evaporated to dryncss, dried in the water oven and weighed until constant, then ignited and weighed again, the latter weight subtracted from the former gave the weight of organic matter extracted from 1 gram of hops.


Mr. Julian L. Baker asked if Mr. Heron had carried out any experiments on the extraction of hops with very dilute aqueous solutions of mixed salts such as ordinarily were present in brewing liquors, or if he had confined his experiments solely to extraction with solutions of single salts.

Mr. A. R. Ling said it appeared to him that in the case of so delicate a material as hops, the differences in the extracts obtained with different salt solutions might be due to more advanced decomposition of the constituents having taken place in some instances, and probably that was why distilled water gave the greatest amount of extract, as there was less decomposition in that case.  He thought also the nauseous flavour of the alkaline extracts indicated some effect of the kind on the constituents, due to the alkali.

Mr. John Heron in reply said his experiments were made some years ago, and in getting the details together it occurred to him that he had not made any experiments on the natural brewing waters.  It would be certainly very interesting to make up an artificial brewing water, say on the Burton standard, and try its action upon hops.  He had experimented with a solution of kainit, which entered into the composition of most mixtures for hardening waters, and that gave about the same extract as the other salts singly.  With regard to Mr. Ling’s remarks, he would remind him that the carbonate of soda, carbonate of potash, and carbonate of lime, gave higher extracts than any of the other solutions.  That he attributed to the alkali acting upon the resins.  The average extract obtained all round might be taken at about 18 per cent.  The conclusion he came to was that there was not much in the extractive properties of salts in dealing with hops—not so much as in the case of malt; for they knew that alkaline salts had a considerable influence on malt as compared with other salts.

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